In the past, a gasification and ash melting system has been known as a technique that can widely treat waste, such as incombustible waste, burned residue, and sludge in addition to municipal waste. The gasification and ash melting system includes: a gasification furnace that gasifies waste by thermally decomposing the waste; a melting furnace that is provided on the downstream side of the gasification furnace, combusts pyrolysis gas generated by the gasification furnace at high temperature, and converts ashes contained in the gas into molten slag; and a secondary combustion chamber that combusts flue gas discharged from the melting furnace. For the purpose of the recycling, volume reduction, and detoxification of waste, the gasification and ash melting system extracts slag from the melting furnace to reuse the slag as materials of construction such as base course materials or recovers waste heat from flue gas discharged from the secondary combustion chamber to generate electricity.
A fluidized bed gasification furnace is widely used as the gasification furnace of such a gasification and ash melting system. A fluidized bed, in which a fluid medium is fluidized by the supply of combustion air, is formed at the bottom of the fluidized bed gasification furnace, and the fluidized bed gasification furnace is a device that partially combusts the waste put in the fluidized bed and thermally decomposes the waste in the fluidized bed maintained at high temperature by the combustion heat.
Further, the fluidized bed gasification furnace is configured to discharge incombustibles from the bottom of the gasification furnace together with sand that is a fluid medium. Since the gasification melting facility requires volume reduction as described above, it is important to reduce the volume of incombustibles to be ultimately buried and treated. Means for reducing the volume of incombustibles, which are to be finally buried and treated, by recovering valuable metal, such as iron or aluminum, from incombustibles, and the like are known as means for reducing the volume of incombustibles.
A gasification melting facility that pulverizes incombustibles from which valuable metal has been removed and introduces the pulverized incombustibles into a melting furnace to melt the pulverized incombustibles is disclosed in Patent Document 1 as means for reducing the volume of other wastes. This gasification melting facility can introduce the incombustibles into the melting furnace by pulverizing the incombustibles after further removing metals (metals other than valuable metal) from the incombustibles, from which valuable metal has been removed, using a vibrating screen and by cutting out a fixed amount of the pulverized incombustibles.